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Narrator:Listen to part of a lecture in a geology class.
独白:听下面一段地质学课堂演讲
Professor:As geologists, we examine layers of sediment on the Earth's surface to approximate the dates of past geologic time periods.
教授:作为地质学家，我们检查地球表面的沉积层来评估过去地质时期的年代。
Ah sediment as you know i s material like sand, gravel, fossil fragments that is transported by natural processes like wind, water flow or the movement of glaciers.
呃，沉淀物就是一些像沙子、碎石、化石脆片等物质，由自然过程如风、流水或者冰川移动等进行转移。
So sediment is transported and then deposited and it forms layers on the Earth's surface over time.
沉淀物被转移然后沉积，并随着时间的流逝在地球表层形成层。
We examine these layers to learn about different geologic time periods including when they began and ended.
我们研究这些层来得知不同地质时期的信息，包括它们的起止时间。
For example, from about 1.8 million years ago to around 11 thousand years ago was the Pleistocene epic.
比如，从大约 180 万年前到 11,000 年前左右是更新世时期。
The Pleistocene epic was an ice age.
更新世时期是冰河时期。
During this epic, sediment was made by the kind of erosion and we athering that happens when the climate is colder, and part of those sediments are fossils of plants and animals that lived at that time.
在这个时期，沉淀物是由腐蚀物构成，我们推断当时气候更加寒冷，沉淀物中的一部分是当时动植物的化石。
The Holocene epic followed the Pleistocene epic when the Earth's climate warmed up around 11 thousand years ago.
全新世时期在更新世之后，是在大约11,000 年前气候开始变暖的阶段。
The Holocene epic is characterized by different sediments, ones that form when the climate is warmer.
全新世沉积物的特征是各种各样，都是在气候变暖后形成的。
Because the climate changed, the types of plants and animals changed also.
由于气候变化，动植物的类型也有所变化。
Holocene sediments contain remnants of more recent plants and animals, so it's pretty easy to differentiate geologically between these two epics.
全新世沉淀物包含了更接近现代的动植物的残骸，因此在地质上也很好区分这两个时期。
Now there is growing evidence that the presence of humans has altered the earth so much that a new epic of geologic history has begun-the Anthropocene epic, a new human-influenced epic.
现在有越来越多的证据显示人类的存在已经很大程度上的改变了地球，以至于开始了地质历史的一个新纪元-人类世，一个全新的人类主导的时期。
This idea that we've entered a new Anthropocene epic was first proposed in 2002.
我们进入人类世的这种说法第一次是在 2002 年提出。
The idea is that around the year 1800 CE the human population became large enough, around a billion people, that its activities started altering the environment.
这种说法是说在大约 1800 年人类人口已经足够多，达到 10 亿左右，人类的活动已经改变了环境。
This was also the time of the industrial revolution, which brought a tremendous increase in the use of fossil fuels such as coal.
这也是工业革命时期，人类使用煤等化石燃料也大幅度上升。
The exploitation of fossil fuels has brought planet wide developments:industrialization, construction, uh, mass transport.
对化石燃料的开发给地球带来了广泛的发展，工业、建筑，还有大宗运输。
And these developments have caused major changes like additional erosion of the Earth's surface and deforestation.
而这些发展就引发了巨大的变化，如地球表面额外的腐蚀以及森林采伐。
Also, things like the damming of rivers, has caused increased sediment production, not to mention the addition of more carbon dioxide and methane in the atmosphere.
同样，像给河筑坝，也会导致沉积物的增加，更不要说大气层中更多的二氧化碳和甲烷了。
Naturally all these changes show up in recent sediments.
很自然的这些变化就会在近期的沉淀物中展现出来。
And these sediments are quite different from pre year 1800 sediment layers.
这些沉淀物与 1800 年前的沉积层有很大不同。
Interestingly there's some speculation that humans started having a major impact on Earth much earlier, about 8000 years ago.
有趣的是，还有一种猜测是人类早在 8000 年前就对地球产生了巨大的影响,
That's when agriculture was becoming widespread.
也就是农业开始广泛开展的时期。
Early farmers started clearing forests and livestock produced a lot of extra methane.
早期的农民开始清除森林和家畜来生产出大量额外的甲烷。
But I want to stress this is just a hypothesis.
但是我想强调一下这只是一个猜想。
The idea that early humans could have had such a major effect, well I'm just not sure we can compare it with the industrial age.
这种早期人类造成的巨大影响的说法，我只是不确定能否将它与工业时期来相比。
Geologists in the far future will be able to examine the sediment being laid down today, whereas right now we can say that yes, human impact on the Earth is clear:
未来的地质学家将能检查今天的沉积物，然而现在我想说的是，人类对地球的影响是显而易见的，
It'll be future researchers who have better perspective and will be able to really draw a line between the Holocene and the Anthropocene epics.
但是将来的研究人员会有更好的视角并能将全新世与人类世划分开来。
